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Patterns of Inheritance

Patterns of Inheritance. Chromosomes. Karyotype: Entire set of chromosomes from a single cell Chromosomes. Each double DNA helix is packaged into a chromosome. Every species has a particular number of chromosomes Hereditable information exists in discrete units called genes

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Patterns of Inheritance

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  1. Patterns of Inheritance

  2. Chromosomes • Karyotype: Entire set of chromosomes from a single cell • Chromosomes. Each double DNA helix is packaged into a chromosome. • Every species has a particular number of chromosomes • Hereditable information exists in discrete units called genes • A gene is the specific portion of chromosome that has the complete information to synthesize … a specific protein

  3. Gregor Mendel • Before settling down as a monk in the monastery of St. Thomas in Brünn. • Gregor Mendel tried his hand at several pursuits, including health care and teaching. • He studied botany and mathematics among other subjects. This training proved crucial to his later experiments, which were the foundation for the modern science of genetics.

  4. Although Mendel worked without knowledge of genes or chromosomes, we can more easily follow his experiments.

  5. Genetic concepts • A gene´s specific physical location on a chromosome is called locus (plural, loci). • Homologous chromosomes carry the same genes, located at the same loci. • Alternate forms of the gene, is called alleles. • If both homologous chromosomes in an organism have the same allele are a given gene locus, the organism is said to be homozygous at the gene locus • If two homologous chromosomes have different alleles at a given locus, the organism is heterozygous.

  6. The M locus contains the M gene, which is involved in determining leaf color. Both chomosomes carry the same allele of the M gene. This tomato plant is homozygous for the M gene. Pair of homologous chromosomes The D locus contains the D gene, which is involved in determining plant height. Both chromosomes carry the same allele of the D gene.This tomato plant is homozygous for the D gene. The Bk locus contains the Bk gene, which is involved in determinig fruit shape. Each chromosome carries a different allele of the Bk gene. This tomato plant is heterozygous for the Bk gene.

  7. Mendel´s results, allow us to develop a five-part Model: 1. Each trait is determined by pairs of discrete physical units (alleles), which we now call genes. Each individual has two genes for a given trait. 2. Pairs of genes on homologous chromosomes separate from each other during gamete formation, so each gamete receives only one allele of an organism´s pair of genes. This conclusion is known as Mendel´s law of segregation. Each gamete receives only one of each parent´s pair of genes for each trait.

  8. 3. Which member of a pair of genes becomes included in a gamete is determined by chance. 4. When two alternate forms of a gene are present, one (the dominant allele) will mask the expression of the other (the recessive allele). 5. True-breeding (all the offspring produced are identical to the parent plant) organisms have two of the same alleles for a given trait.

  9. Mendel´s model • Using letters to represent the different alleles, we will assign the uppercase letter P (dominant allele) to the allele for purple and the lowercase letterp (recessive allele) to the allele for white. • Purple-flowered plant has two alleles for purple (PP), whereas a white-flowered plant has two alleles for white (pp). All the sperm and eggs produced by a PP plant carry the P allele; all the sperm and eggs of a pp plant carry the p allele.

  10. P P p p P P p p P P F1 p p Result: 100% P

  11. | PP Gametes from F1 plantsF2 offspring Sperm eggs + P P Pp P p + Pp p P + pp p p +

  12. P P P p P p p p p P F2 P p Results: 75% P, 25% p

  13. Therefore, three types of offspring can be produced: PP, Pp, and pp. The three types occur in the approximate proportions of 1/4 PP, 1/2 Pp, and 1/4 pp. • The actual combination of alleles carried by an organism (for example, PP or Pp) is its genotype. • The organism´s traits, including its outward appearance, behavior, digestive enzymes, blood type, or any other observable feature, make up its phenotype.

  14. P p P P p P P P P p P P Punnet SquarePPxPp Result: 100 % P (Phenotype) Result: 50 % PP, 50 % Pp (Genotype)

  15. p P p P p p p p P p p p Result: Genotype: 50% Pp, 50 % pp Result: Phenotype: 50 % P, 50 % p Punnet SquarePpxpp

  16. Mendel´s Hypothesis can be used to predict the outcome of new types of single-trait crosses. • Mendel hypothesized that genes on different chromosomes are inherited independently.

  17. Problem 1 • Your Grandmother (mother side) is diabetic (Recesive) and so is your Grandfather (Father side). • A) What are your chances of being diabetic if both of them got married with a normal homozygous? • (Hint: You must do first your parents.)

  18. Problem 1b • Your Grandmother (mother side) is diabetic (Recesive) and so is your Grandfather (Father side). • b) What are your chances of being diabetic if your Grandfather (mother side) is a normal heterozygous and your Grandmother (Father side) is a normal homozygous?

  19. Problem 1.c • Your Grandmother (mother side) is diabetic (Recesive) and so is your Grandfather (Father side). • C) What are your chances of being diabetic if both of them got married with a normal heterozygous?

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